Compliance to Plan in Open Pit Mining

Compliance to Plan has proven to be one of the most significant Key Performance Indicators (KPI) in mining. Compliance to Plan is all about tracking and assessing the correlation between what is mined operationally on the ground (actual data) versus what was planned (planned data) to be mined in a specific period. This is performed mainly to report spatially and quantitatively, the material that was Planned and Mined, Planned and Not Mined as well as Mined and Not Planned.

As it was discussed on the "Compliance to Design" article, the success of a mine to a certain extent is dependent on the following key components:  the quality and integration of the plans in place (from long to short-term) and the execution of the defined plans. It is essential to structure the shorter-term operational plans and activities in such a way that the mine can obviously be in a position to meet the operational and financial targets. It is even more important to ensure that the shorter-term operational plans and activities are executed in a manner that will not compromise mine’s capability to deliver on the defined long-term plan. For me, this is where most open pit mines get it wrong – completely diverging from the long-term plan in order to satisfy short-term targets e.g., reducing the required amount of waste stripping (quantitative) or mining out of sequence (spatial).

The most dominant approach used in the mining industry to track and measure plan adherence involves completely treating the Compliance to Plan KPI as a time-based or temporal KPI e.g., tracking the tonnage produced/mining costs incurred in a specific period of time. Most operational mines place huge prizes (production bonuses-you know what I am talking about ??) on achieving the temporal KPIs at the expense of spatial compliance. Spatial compliance assesses how well the mine plan is executed on the 3D space. The downfall of relying only on temporal KPIs is that one can always achieve positive temporal KPIs month-in and month-out, while what happens spatially on the ground is a different story altogether. Therefore, spatial compliance is a critical component of the Compliance to Plan KPI and should be treated as such. I mean, achieving your short-term temporal KPIs while mining in the wrong areas spatially might lead to the mine not fully realising the defined long-term value, or even worse, completely sterilising the mineral resource. The opposite is also true – mining in the right areas but failing to achieve the temporal KPIs can also manifest over time, resulting in the mine not fully realising the defined long-term value.

When you are using mine planning solutions like Datamine’s Studio OP, you are able to measure and reconcile between the planned and actual data with ease. The methodology involves defining three surfaces: the reference surface (starting point for the reconciliation), the current surveyed pit surface (actual surface) and the End of Period pit surface (planned surface) shown on Figure 1below.

Figure 1: Surfaces used to assess Compliance to Plan

These three surfaces can be used to identify the areas that have been Planned and Mined (green), Mined not Planned (red) and Planned not Mined (blue) shown on Figure 2 below. This gives you a clear indication of the spatial compliance and areas of poor adherence that you may need to urgently fix. When you run the analysis with a block model, you will also be able to pull out quantitative information like Tonnes and grades as well to track against your temporal KPIs in place.

Figure 2: Spatial check for areas that are Planned and Mined, Mined not Planned and Planned not Mined

More advanced operations have been interested in breaking down the Mined not Planned areas into areas that are Mined out of sequence and areas that are Mined out plan. For you to bring into attention the areas mined out of sequence and out of plan, you need to define a 4th surface which represents the total area anticipated to be mined after a certain period (annual, 5 year etc) as shown on the Figure 3 below. Let us assume the 4th surface defined on the figure below represents the Planned End of Budget Plan surface.

Figure 3: Addition of the fourth surface to Compliance to Plan check

An area is deemed to be mined out of sequence if it mined out of the planned End of Month pit surface, but it is still within the planned End of Budget Plan surface (orange area on Figure 4). This means that you have mined ahead of the plan, and you can still correct the deviation to ensure that at the end, you are aligned with the budget plan surface. An area is said to be mined out of plan if the mining happens outside of both the End of Month and End of Budget Plan Surfaces (red area on the Figure 4). It is important to identify the areas (quantity and spatial) in order to have a better shot at correcting the deviations.

Figure 4: Compliance to Plan showing areas Mined out of sequence and areas Mined out of Plan

I have been over-emphasising the importance of tracking and reconciling the planned and actual data. If you want to improve and rectify any deviations that is reported from the planned vs. actual reconciliation, you need to have a good understanding of the causes of deviations in the first place. Based on what was discussed above, the deviations mainly include failure to achieve the temporal KPIs, failure to adhere to spatial compliance and a combination of the two

Failure to achieve the quantitative, temporal KPIs

Short-term plans are focussed on the extraction tactics and allocation of resources (human and equipment) in order to achieve the long-term plan. Numerous assumptions are made when developing and modelling the short-term plans. Some of the common assumptions include equipment availabilities and utilisations, mining and hauling rates etc. These assumptions can affect the production rates directly or indirectly. Any major under/overestimation could result in a significant deviation between the planned and actual production rates. Spatially, mining activities are still happening in the correct, planned areas but the targeted temporal KPIs such as total waste stripping are not achieved. It is important to fix this to ensure that the short-term plans realise the value defined in the long-term plan.

Failure to adhere to Spatial execution

Remember, spatial compliance assesses how well the mine plan is executed on the 3D space. So, failure to adhere to spatial execution means that the mining activities are not happening in the correct, planned areas. This results in a lot of areas that are Planned for mining but are actually not mined (Planned not Mined). Failure to adhere to spatial compliance usually happens when priority is placed on the short-term objectives (reducing unit cost of mining, targeting high grade ore only etc.) to the detriment of spatial execution. Sometimes it happens due to certain operational issues (poor dewatering) which results in mining takin place in areas that were not planned. It is important to correct this because it could manifest and progressively result in mining activities actually taking place out of plan in future.

Drawing back to the article titled “Don’t give up yet. There is a way to optimise your waste dumping schedule”, I did highlight the importance dumping to plan as well. It is important to ensure that you mine the planned waste tonnages and you spatially dump them at the correct places as well. The days of relying only on Temporal KPIs (waste tonnes mined) are long behind us. It is just as important to ensure that waste is spatially placed at the correct, planned locations.